The invention relates to the field of disposable biomedical electrodes for establishing an electrical connection between the skin of the human anatomy and an electromedical apparatus such as a high impedance electromyograph, electrocardiograph, electrostimulator for pain relief and the like. More specifically, the present invention is directed to a disposable biomedical electrode having a secured one-piece conductive terminal which is formed using less material, resulting in decreased manufacturing expenses. The biomedical electrode can also include an improved electrolytic gel which provides more comfort for the patient while maintaining electrical performance.
Many types of disposable biomedical electrodes have been introduced in recent years. Typically they comprise: (1) a metallic or electrically-conductive carbon terminal member having means for electrical connection to an electromedical apparatus such as an electrocardiograph; (2) an adhesive tape or pad for holding the terminal member in place on the skin; and (3) an electrically-conductive, conformable interfacing material such as an electrolyte gel or paste over the surface of the terminal member which contacts the skin to reduce skin impedance and to improve electrical contact between the skin-and the terminal member.
Disposable biomedical electrodes have been improved in the last few years by the introduction of electrically-conductive, pressure-sensitive adhesives to replace conventional electrolyte gels and creams. Such gels were generally unpleasant to use and, because of their high water content, required elaborate packaging to prevent "dry-out" problems. The electrically-conductive, pressure-sensitive adhesives are not as comfortable for patients when attached to their skin in that they do not provide a soothing or moist feeling and hair tends to be torn away from the patient's body upon removal of the electrode. It would be desirable, therefore, to have a disposable biomedical electrode which includes an electrolyte gel which is more comfortable for the patient, yet does not experience "dry-out" problems or reduced electrical performance.
For ease of connection to the lead wire of an electromedical device, the terminal member of many disposable biomedical electrodes is formed in the shape of the male portion of a snap fastener adapted to engage the female portion of the snap fastener attached to the lead wire of the electromedical device. Such a terminal member comprises a flat, circular portion and a knob-like projection extending perpendicularly therefrom. A one-piece terminal member of this type is difficult to anchor securely to the adhesive pad. If the terminal member is not securely anchored to the other components of the disposable electrode, it may pull out when force is applied to disconnect the terminal member from the female portion of the snap fastener.
To avoid this problem, a two-piece terminal member is typically used in the art comprising a so-called "stud and eyelet"arrangement. The stud comprises a flat circular portion and a pin-like member extending perpendicularly therefrom. The stud is inserted into an eyelet comprising a hollow knob having a circular base. Adhesive tape or a stiffening piece used to reinforce the adhesive tape is sandwiched between the stud and the eyelet. After the stud is inserted into the eyelet, the eyelet is crimped at its neck to ensure good electrical contact between the stud and eyelet and to anchor the adhesive tape or stiffening piece securely. Alternatively, the stud can be friction- fitted within the eyelet without crimping. The two-piece terminal member as described above suffers from a number of disadvantages including potential corrosion problems if the stud and eyelet are made from dissimilar metals, high electrical resistance between the stud and eyelet, and increased difficulty and cost of manufacturing.
Because of the disadvantages associated with the two-piece terminal member, particularly its high cost, a number of attempts have been made to solve the anchoring problems encountered with one-piece terminal members so that the latter might be more suitable for disposable biomedical electrodes. For example, a retaining ring which fits over the projecting portion of the terminal member to mechanically secure the adhesive tape to the flat base portion of the terminal member has been used in the past. Further, Corasanti, U.S. Pat. No. 4,029,086, describes a disposable biomedical electrode having a one-piece terminal member in which the projecting portion thereof contains a ridge over which a washer is snapped to secure the terminal member to the adhesive pad.
In general, the prior art methods of anchoring one-piece terminal members to the other components of the electrodes have involved a friction-fit washer or retaining ring which is mechanically biased against the stem of the knob-like projection of the terminal member. Although such methods of anchoring generally produce Satisfactory anchoring of the terminal member to the electrode, they complicate the manufacture of the electrode and increase its cost. Thus, it would also be desirable to have a biomedical electrode with a design that includes a one-piece terminal member secured therein without washers, retaining rings and the like which complicate the manufacturing scheme.
Accordingly, there is need in the art for a disposable biomedical electrode which includes an electrolyte gel that is comfortable for the patient but does not experience the aforementioned "dry-out" problems or decreased electrical performance of prior devices. Additionally, there is a need for such a biomedical electrode which includes a one-piece terminal member secured therein without the need for washers, retaining rings and the like which complicate the manufacturing of such electrodes and thereby increase their cost.